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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Dec
6
revised SHA1 Collisions - what about practical attacks?
More references
Dec
6
revised SHA1 Collisions - what about practical attacks?
Detail how to find Na and Nb product of two primes, or deal with more primes
Dec
6
revised SHA1 Collisions - what about practical attacks?
N in the second attack must be squarefree
Dec
6
revised SHA1 Collisions - what about practical attacks?
Estimation of work involved in the second attack
Dec
6
revised SHA1 Collisions - what about practical attacks?
Polish
Dec
6
comment SHA1 Collisions - what about practical attacks?
@crypto-learner: I now give a lot more details, especially for the second example.
Dec
6
revised SHA1 Collisions - what about practical attacks?
Expand, especially the second example
Dec
5
revised Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
Incorporated the lack of backtracking resistance in the assessement of ANSI931_AES256
Dec
5
revised SHA1 Collisions - what about practical attacks?
More details on the second example. Move the description of collision search in the first example, because it does not quite apply to the second.
Dec
5
revised SHA1 Collisions - what about practical attacks?
Polish
Dec
5
revised Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
Update per Gilles comment
Dec
5
comment Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
@Gilles: yes, in some uses the lack of backtracking resistance can be an issue. I semi-consciously worded the hypothesis of my endorsement so that it excludes this concern, but in retrospect should have mentioned it. You did, very well.
Dec
5
revised SHA1 Collisions - what about practical attacks?
add link; polish
Dec
5
answered SHA1 Collisions - what about practical attacks?
Dec
5
revised Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
Remove duplicate text. State what I think of ANSI931_TDES3 for new developments.
Dec
5
answered Will X9.31 remain a secure & acceptable deterministic random generator beyond 2015?
Dec
4
revised Using machine-learning techniques for data-dependent operations in ciphers
Fix title
Dec
3
comment practical use of homomorphic encryption
Mental poker (in the setup where $n$ is composite) arguably uses the homomorphic properties of RSA.
Dec
3
revised Existential Forgery on textbook RSA signatures
TeXify
Dec
3
comment Existential Forgery on textbook RSA signatures
You can be made right, if you properly define $m' = m_1/m_2$ and $σ' = σ_1/σ_2$, and handle the possible case of these quantities being undefined; by showing that it is extremely unlikely; or/and showing that should it occur nevertheless, the adversary can trivially forge any signature. $\;$ Hint: you need to amend $σ' = σ_1\cdot σ_2$ in a similar way, if you use (as you seem to do) that the definition of a valid signature $σ$ of message $m$ is that $σ=m^d\bmod N$, or the more usual and equivalent definition that $0\le σ<N$ and $σ^e\equiv m\pmod N$.